The present invention generally relates to the field of thermal sciences, and more particularly to heat engines for waste heat recovery.
A heat engine is a device that takes energy from a heat source and converts some of the heat energy into work while rejecting the remaining heat energy to a heat sink. An example of a heat engine is the Rankine cycle-type heat engine represented in FIG. 1.
The thermal efficiency of a heat engine is highly dependent on the difference in temperature between the heat source and the heat sink. When this temperature difference is small, a heat engine's efficiency is low. Because the heat sink temperature is typically fixed by the temperature of the environment, it is desirable to use a heat source with as high of a temperature as possible. However, in waste heat recovery applications, the heat source temperature is also fixed by the temperature of the waste heat. This fixes the thermal efficiencies of waste heat recovery machines to values which are typically small. An economical means to improve the efficiency of waste heat recovery machines is desirable because the initial investment for a machine with low efficiency should not be very large.